As I approached their enclosure late in the day, this view of the resting lions underneath the "Can you see any lions? ..." notice, made me smile :)
I should point out that it's not at all uncommon for the lions at Whipsnade to be so close to the glass. There may be other reasons, but I suspect a major one is that the area is a sun-trap in the enclosure, which itself is situated in quite an exposed part of the Zoo.